Japan's DoCoMo tries to simplify handsets with RF MEMS

PORTLAND, Ore.  MEMS technology is critical to the success of future of wireless handsets, according to an executive with the wireless subsidiary of Japanese carrier NTT.

DoCoMo's Shoichi Narahashi

In a presentation during the MEMS Executive Congress (Sonoma, Calif.), Shoichi Narahashi, an executive with DoCoMo Research Laboratories, made the case for using MEMS RF switches to simplify the bill-of-materials for future mobile handsets. Narahashi said a single, reconfigurable power amplifier chip could replace the four separate amplifier chips required today.

"Reconfigurable [power amplifiers] using MEMS RF switches have the potential to perform just as well as multiple PAs, but at a fraction of the cost and in a more compact form factor," said Narahashi.

DoCoMo showed its prototype design for a quad-band mobile handset that uses two sets of MEMS RF switches: one set to reconfigure a power amplifier to transmit at one of four different frequencies and another that switched in different filters to reconfigure the RF front-end to receive at one of four different frequencies.

Design strengths and weakness were described by Narahashi, but he did not reveal DoCoMo's MEMS supplier, if any.

Nevertheless, "this was the first formal interaction NTT DoCoMo has had with the MEMS industry," said Karen Lightman, managing director of the MEMS Industry Group.

Narahashi claimed DoCoMo's prototype proved the concept, but it is up to MEMS vendors to demonstrate that low-cost RF switches can be fabricated with sufficient power-handling capability. Durability is also needed at a level that matches that provided by multiple amplifiers, he added.